The idea that nerve cells individually produce and release a single neurotransmitter chemical from all their terminals has been a simplifying concept for much of neuroscience for several decades. The recent findings that some nerve cells apparently produce more than one substance with the capacity to act on other nerve cells and muscles, and further that some of these substances are peptides quite unlike the established neurotransmitters, have provoked a number of questions about the basic mechanisms of communication and integration in the nervous system. We have discovered two pairs of readily identifiable neurons, B11 and B12 in the central nervous system of the gastropod mollusk, Tritonia which apparently produce and release at least two neuroactive agents. One of these agents i acetylcholine and the other is at least one peptide. The relatively simple nervous system of Tritonia contains unusually large neurons which can be stimulated and recorded intracellularly, and permits analysis of specific electrical and chemical interactions between nerve cells. It is also possible to determine the role played by the individual neurons in the behavior of the intact animal. In this proposal, experiments are described to confirm our initial findings that B11 contain and use, either separately or in combination, acetylcholine and peptide neurotransmitters. As well, we will try to determine the function of these neurons in behavioral and cellular terms.